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RCruz 15th January 2013 05:34 PM

2SK170BL Vp
After building a rig to measure 2SK170BL Idss and Vp, I am slightly puzzled by the measured results.

The rig consists on a 100 oh resistor in series with the Gate and Source pins (shorted together), where I measre Idss using a 9v bat over the fet.

The Vp rig uses a 1M ohm resistor for Rs and the gate to gnd.

The values I got are:
Idss Vp
6,32 -0,58
6,33 -0,57
6,55 -0,58
7,33 -0,63
7,47 -0,62
7,98 -0,66
8,14 -0,64
8,28 -0,64
9,16 -0,69
10,04 -0,71
10,39 -0,73

Looking at the K170 datasheet, I was convinced that for a 8mA Idss, I would get Vp near -0.45V and not -0.64V as per my measurements.

I am writing this hoping to get some input from other experienced people that might helpme understand this issue.


merlin el mago 15th January 2013 05:40 PM

Ricardo to be sure I will use a bench psu instead the battery.


RCruz 15th January 2013 07:54 PM

Yes, but the results are very consistent.

I want to use the actual Vp for the k170 to build a common source jfet amp calculator :)

stinius 15th January 2013 08:50 PM

1 Attachment(s)

Originally Posted by RCruz (
I was convinced that for a 8mA Idss, I would get Vp near -0.45V and not -0.64V as per my measurements.

Are you sure?

RCruz 16th January 2013 07:17 AM

Thank you stinius.... I was not looking at the correct graph.

So I can assume the relation between Vp nd Idss is fairly linear.... I will do a regression with my data and ee if I can duplicate that plot. :)

RCruz 16th January 2013 07:40 AM

1 Attachment(s)
Here it is

RCruz 21st January 2013 05:50 PM

1 Attachment(s)
And finally the calculator.....

Please take it with a grain of salt regarding Gain calculations.

Hoping for good comments.

bear 21st January 2013 08:32 PM

The assumption that you have a genuine Toshiba part, may or may not be valid.

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